It is known to fabricate structural parts for building walls from concrete using modular stay-in-place forms. Examples of such modular stay in place forms include those described in US patent publication No. 2005/0016103 (Piccone) and PCT publication No. WO96/07799 (Sterling). A representative drawing depicting a partial form 28 according to one prior art system is shown in top plan view in FIG. 1. Form 28 includes a plurality of wall panels 30 (e.g. 30A, 30B, 30C, 30D), each of which has an inwardly facing surface 31A and an outwardly facing surface 31B. Each of panels 30 includes a terminal male T-connector component 34 at one of its transverse, longitudinally-extending edges (longitudinal being the direction into and out of the FIG. 1 page) and a terminal female C-connector component 32 at its opposing longitudinal edge. Male T-connector components 34 slide longitudinally into the receptacles of female C-connector components 32 to join edge-adjacent panels 30 to form a pair of substantially parallel wall segments (generally indicated at 27, 29). Depending on the needs for particular wall segments 27, 29, different panels 30 may have different transverse dimensions. For example, comparing panels 30A and 30B, it can be seen that panel 30A has approximately ¼ of the transverse length of panel 30B.
Form 28 includes support panels 36A which extend between, and connect to each of, wall segments 27, 29 at transversely spaced apart locations. Support panels 36A include male T-connector components 42 slidably received in the receptacles of female C-connector components 38 which extend inwardly from inwardly facing surfaces 31A or from female C-connector components 32. Form 28 comprises tensioning panels 40 which extend between panels 30 and support panels 36A at various locations within form 28. Tensioning panels 40 include male T-connector components 46 received in the receptacles of female C-connector components 38.
In use, form 28 is assembled by slidable connection of the various male T-connector components 34, 42, 46 in the receptacles of the various female C-connectors 32, 38. Liquid concrete is then introduced into form 28 between wall segments 27, 29. The concrete flows through apertures (not shown) in support panels 36A and tensioning panels 40 to fill the interior of form 28 (i.e. between wall segments 27, 29). When the concrete solidifies, the concrete (together with form 28) provide a structural component (e.g. a wall) for a building or other structure.
A problem with prior art systems is referred to colloquially as “pillowing”. Pillowing refers to the outward deformation of wall panels 30 due to the weight and corresponding outward pressure generated by liquid concrete when it is introduced into form 28. Pillowing may be reduced to some degree by support panels 36A and tensioning panels 40 which connect to wall panels 30 at female C-connector components 38. Despite the presence of support panels 36A and tensioning panels 40 and their connection to wall panels 30 at connector components 38, wall panel 30 may still exhibit pillowing. By way of example, pillowing may occur in the regions of panels 30 between support panels 36A, tensioning panels 40 and their corresponding connector components 38. FIG. 2 schematically depicts the pillowing of a prior art wall panel 30 at regions 52A, 52B, 52C between support panels 36A, tensioning panels 40 and their corresponding connector components 38. The concrete (not explicitly shown) on the inside 54 of panel 30 exerts outward forces on panel 30 (as shown at arrows 56). These outward forces tend to cause deformation (or pillowing) of panel 30 at regions 52A, 52B, 52C. In addition to the pillowing at individual regions 52A, 52B, 52C, the outward force on panel 30 can cause outward (in direction 56) pillowing of the entire transverse width of panel 30 (i.e. between the transverse edges of panel 30).
Another problem with prior art systems is referred to colloquially as “bellying”. Bellying refers to another type of outward deformation of wall panels due to the weight and corresponding pressure generated by liquid concrete when it is introduced into form 28. Bellying typically occurs near the middle of the vertical dimension of a wall formed from concrete. In contrast to pillowing, which creates convexities along the transverse dimensions of panels 30 (as shown in FIG. 2), bellying creates convexities along the vertical dimensions of panels 30.
Deformation of panels due to the weight of liquid concrete can lead to a number of related problems including, without limitation, unsightly wall appearance, panel fatigue, reduction in structural integrity and/or the like.
There is accordingly a general desire to provide modular stay-in-pace formwork components that minimize and/or otherwise reduce (in relation to the prior art) outward deformation of panels under the weight of liquid concrete.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.